Some WiFi location techniques rely on receiving GPS data paired with WiFi scans from a large set of devices. The received data is then used to determine the location of wireless or WiFi access points (WAPs). Once the location of WAPs are known, WiFi enabled devices can perform WiFi scans and use a database of known access point locations to compute the locations of the WiFi enabled devices.
One shortcoming of the GPS based approach is that it typically cannot accurately determine the location of wireless access points for areas where GPS is unavailable, such as in indoor environments and urban canyons. This lowers both the accuracy and coverage of a WiFi access point database especially since the majority of access points are indoors, yet many of them cannot be seen at all outdoors or can only be seen with a very weak signal strength. This makes it difficult to compute an accurate location for an access point in areas where GPS is unavailable, thereby making it difficult to accurately compute and determine the location of a WiFi enabled device in those areas.